The US study also indicated that diet soft drink fans were 2.9 times more likely to develop Alzheimer's. But after accounting for all lifestyle factors, the researchers found the link to dementia was statistically insignificant, however, the impact on stroke risk remained.

The study, which looked at ten years' worth of data from more than 4,300 people, indicates that people need to look beyond the word 'diet' when making drink choices.

"Drinking at least one artificially sweetened beverage daily was associated with almost three times the risk of developing stroke or dementia compared to those who drank artificially sweetened beverages less than once a week," the research read, which was published in Stroke, the journal of the American Heart Association.

"To our knowledge, our study is the first to report an association between daily intake of artificially sweetened soft drink and increased risk of both all-cause dementia and dementia because of Alzheimer's disease," the co-authors added.

THE PROBLEM WITH THE 'NO CALORIES' TRADEOFF:

Diet drinks contain next-to-no calories, because they use artificial sweeteners that are hundreds, sometimes thousands of times sweeter than sugar.

There is public concern about some sweeteners, with scientists across the world arguing that low-calorie substitutes may lead to weight gain and increase the risk of developing type 2 diabetes.

"A lot of people assume they must be healthy choices because they are not sugared beverages, but the critical thing for people to understand is we don't have the evidence," Prof Susan Swithers, from the US's Purdue University told the BBC.

Typically, the different types of sweeteners used in diet drinks range from Aspartame, Saccharine and Stevia.

Aspartame is the sweetener most used in diet drinks, and is also the most controversial.

At 200 times sweeter than sugar, it is used right across the world as a sugar substitute, including cereal, chewing gum and lollies.